Probably the best construction materials are the ecological ones. However, depending on the region, local variants are perhaps better used (more widely available, replacable, ...). Certains buildings (silo's, domes (for sleeping), and the composting toilet tower can be made from trees (which are grafted so as to form a single tree). See http://www.bloomberg.com/apps/news?pid=20601130&sid=a.hwYnFfAoDE

Certain (industrial) buildings and towns can be cheap to obtain. See Cheap acquiring of towns and large buildings. Also ships can be obtained and made for living in (houseboats). They have the advantage that they are float and that they are movable. Areas prone to storms (Pacific/Caribbean region) and altering weather patterns might better chose for this option if they are presented the choice. Finally, a last advantage can be that if microgeneration, and sanitation, ... equipment are mounted on the boat (similar to the approach followed by GeWOONboot), the equipement too is protected and all available at a single location. See Cheap acquiring of ship